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1. (WO1998050250) SEAT ADJUSTMENT MECHANISM
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SEAT ADJUSTMENT MECHANISM

The present invention relates to vehicle seating, and in particular to height and tilt adjustment mechanisms for such seating. Throughout this specification, the expressions "height" and "tilt" in relation to a vehicle seat refer to the height and tilt of the seat base (upon which the user sits) above the vehicle floor, whether the seat backrest is independent of such seat base positioning or not.

There are numerous mechanisms in the prior art for the height adjustment of vehicle seats, and also numerous mechanisms for the separate adjustment of the tilt of the vehicle seat.

Typical simple prior art mechanisms include a single, combined height and tilt adjustment mechanism in which the action of raising the seat also causes the seat to tilt forward to a degree which is dependent upon the degree of height adjustment. Whilst this has advantages in simplicity, it does not offer optimum performance for all users of the seat.

Other prior art mechanisms include separate height and tilt mechanisms which are necessarily more complex and less convenient to adjust. Often, height and/or tilt is continuously adjustable by way of a screw jack type arrangement in which the user must wind a handle through many turns in order to achieve the desired seat position. The seat retains its selected height and/or tilt against the pressure from the occupant's weight simply through the gearing of the handle. A disadvantage of this arrangement is that the adjustment mechanism is slow to use.

Other well-known adjustment mechanisms provide a seat which is adjustable to a plurality of discrete positions by the release and subsequent re-engagement of a pin into one of a plurality of slots in a toothed plate or the like. A disadvantage of this arrangement is that the seat can only be adjusted to a relatively small number of discrete settings.

It is an object of the present invention to provide a combined height and tilt adjustment mechanism for a seat, in which both the height and tilt are separately adjustable to an infinite number of positions between two extremes.

It is a further object of the present invention to provide a combined height and tilt adjustment mechanism for a seat which is both quick and simple to use.

It is a further object of the present invention to provide a combined height and tilt adjustment mechanism for a seat which is simple in construction to reduce manufacturing costs.

It is a further object of the present invention to provide a combined height and tilt adjustment mechanism for a seat which offers a low profile when at its lowermost setting.

Embodiments of the present invention will now be described by way of example, and with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a seat height and tilt adjustment mechanism according to the present invention, including a seat base frame and seat slides;

Figure 2 shows a plan view of the seat adjustment mechanism of figure 1;

Figure 3 shows a front view of the seat adjustment mechanism of 5 figure 1;

Figure 4 shows a right side view of the seat adjustment mechanism of figure 1 ; and

o Figure 5 shows a right side view of the seat adjustment mechanism as in figure 4 but with the seating slide rails removed to reveal additional detail of the adjustment mechanism.

Throughout the present specification, the expressions "forward" and 5 "aft", "up" and "down", "raise" and "lower" are used for clarity to refer to a seat having a normal orientation within a vehicle. The expressions "left" and "right" hand sides are used as perceived by an occupant of the seat. It will be understood that the functionality of the present adjustment mechanism is not, however, dependent upon its orientation.
0
With reference to figures 1 to 5, a combined seat height and tilt adjustment mechanism 10 is mounted onto a pair of slide mechanisms 11 ,

12 of known type. Each slide mechanism 11 , 12 includes a fixed portion

13 for attaching to the floor of a vehicle using known methods, and a 5 runner portion 14 which is in sliding engagement with the fixed portion

13. A seat base frame 15 is attached to the runners 14 via the combined height and tilt adjustment mechanism 10, thereby allowing adjustment of the seat base frame 15 in both the horizontal plane fore and aft, and in the vertical direction as described hereinafter.
0 The fore and aft adjustment of the seat is in accordance with known slide mechanisms and will not be described further. Many different types of existing slide mechanisms are fully compatible with the present invention.

Each slide mechanism 11 , 12 preferably includes a sidewall 16, 17 which is either integrally formed with the slide mechanism as shown, or attached thereto. The slide mechanisms are each attached to a forward cross-bar 20 and an aft cross-bar 21. Preferably, the cross-bars are attached to the slide mechanisms by longitudinally-extending lugs 22, 23 which locate in slots 24, 25 in the sidewalls 16, 17. Other fixing techniques are well known. Preferably, the cross-bars are formed from pressed steel with longitudinal contours for stiffness and are profiled with curved portions 26, 27 (see also figure 3) to provide clearance beneath the cross-bars for slide mechanism components which are not shown.

Attached to the upper surface of forward cross-bar 20 is a pair of upstanding lugs 30, 31 which each receive a respective pivot 34, 35. Similarly, attached to the upper surface of aft cross-bar 21 is a pair of upstanding lugs 32, 33 which also each receive a respective pivot 36, 37. The lugs may be attached to the cross-bars by welding or other suitable method, or integrally formed therewith. For manufacturing simplicity, both forward and aft cross-bars 20, 21 are preferably identical components.

Attached to forward pivots 34 and 35 is a forward crank 40 which is rotatable about the pivots 34, 35. The crank 40 comprises a crank bar 41 having a first and a second arm 42, 43 at the left and right ends of the crank bar, respectively. The first and second arms 42, 43 provide the connection with pivots 34, 35 enabling the crank 40 to rotate from the position shown in the figures, in a clockwise direction as viewed from the perspective of figures 1 and 4. An intermediate portion 44 of the forward crank bar (see figure 3) is displaced off-axis so that the intermediate portion lies below the level of the forward cross-bar 20. Preferably, the intermediate portion 44 is not laterally centred with respect to the seat, as shown in figure 3.

An identical arrangement comprising aft crank 50, crank bar 51 , and third and fourth arms 52, 53 is connected to the aft cross-bar 21 through pivots 36, 37, although the aft crank 50 is adapted to rotate from the position shown in the figures in an anticlockwise direction as viewed from the perspective of figures 1 and 4. For manufacturing simplicity, both forward and aft crank assemblies preferably comprise identical components, although it will be understood that the aft crank assembly is rotated by 180° in the horizontal plane with respect to the forward crank assembly. Thus, intermediate portion 54 of the aft crank bar 51 is displaced laterally from the corresponding intermediate portion 44 of the forward crank bar enabling other components to be positioned side by side beneath seat as described hereinafter.

Pivotally attached to the first arm 42 and the second arm 43 are, respectively, a first link member 45 and a second link member 46 which are each rigidly attached to and support the forward end of the seat base frame 15. Similarly, pivotally attached to the third arm 52 and the fourth arm 53 are, respectively, a third link member 55 and a fourth link member 56 which are each rigidly attached to and support the aft end of the seat base frame 15.

However, as best viewed in figure 5, a significant difference between the third and fourth link members 55, 56, when compared with the first and second link members 45, 46, is that the connecting pivot 57 between the third link member 55 and the crank 50, and between the fourth link member 56 and the crank 50 is free to travel in a substantially horizontal direction within slot 58, whereas connecting pivot 47 between the first link member 45 and the crank 40, and between the second link member 46 and the crank 40 is constrained so that only rotational motion is possible. The pivot 57 and slot 58 provide the additional degree of freedom required for the seat base frame 15 to be able to tilt with respect to the seating slides 11 and 12.

It will be understood that this degree of freedom could, however, be provided in a number of other ways, for example by allowing the third and fourth link members 55, 56 to also rotate with respect to the seat base frame 15. Other alternatives include providing an additional pivoting link or allowing the seat base frame to be extensible in length.

The intermediate portion 44 of the forward crank bar 40 includes a bracket 60 extending rearwardly therefrom which houses a pivot 61 which forms the connection with the moving end 71 of a first linear positioning device 70. The other, fixed, end 72 of the linear positioning device 70 is coupled, by way of a pivot 66 to a pair of downwardly projecting L-shaped brackets 67 on aft cross-bar 21.

An analogous arrangement is provided, connected to the intermediate portion 54 of the aft crank bar 50, comprising bracket 62 and pivot 63 forming the connection with the moving end 81 of a second linear positioning device 80. The opposite, fixed, end 82 of the second linear positioning device 80 is connected to a pair of downwardly projecting L-shaped brackets 68 on the forward cross-bar 20 by pivot 69. It will again be appreciated that, for manufacturing simplicity, these components are substantially identical to those associated with the first linear positioning device, but rotated through 180° in the horizontal plane.

The linear positioning devices 70, 80 are preferably of the type sold by P L Porter Co as "Mechloks" . (Mechlok is a registered trademark of P L Porter Co.) The linear positioning device comprises an outer casing 73 with an axially displaceable shaft 74 extending at least partly through the casing 73. A helical coil which is internal to the casing 73 and is therefore not shown, is coupled at one end to the inside of casing 73 and is tightly wound around the shaft 74 so as to provide a strong frictional force preventing axial displacement of the shaft. The other end of the helical coil is coupled to a collar (not shown) which is coaxial with the shaft 74.

Rotation of the collar about the shaft axis by perhaps 20 or 30° sufficiently unwinds the helical coil so as to unlock the shaft 74 such that it is freely axially displaceable with respect to the casing. Release of the collar causes the helical coil to return to its position tightly wound around the shaft 74. Each linear positioning device may be provided with pairs of helical coils, within the casing 73, extending along the shaft 74 in opposite directions from the collar so as to increase the holding force available.

A release mechanism 75 is provided on the casing 73 of the linear positioning device 70. Preferably this release mechanism provides a fixed member 76 coupled to the casing 73 and a moving member 77 coupled to the collar. Fixed member 76 is coupled to the outer sheath 92 of a flexible control cable (figure 2) and moving member 77 is coupled to the inner control wire 91 of the flexible control cable 90, in a manner well known in the art.

It will be understood that a series of rigid mechanical linkages could also be used in place of flexible control cables.

In use, it will be understood that release of the first linear positioning device 70 enables the forward crank 40 to rotate about its pivots 34, 35 thereby raising or lowering the height of the forward part of the seat base frame 15, while release of the second linear positioning device 80 enables the aft crank 50 to rotate about its pivots 36, 37 thereby raising or lowering the height of the aft part of the seat base frame 15. The actions of the forward and aft cranks 40, 50 are entirely independent and may be operated separately or in unison.

The advantages of the linear positioning mechanisms as described are that they are compact and offer large extensibility, as well as being lockable in continuously variable positions rather than in discrete steps. The present height and tilt adjustment mechanism can, however, use other types of linear positioning mechanism which may lock in a plurality of discrete positions.

Preferably, a bias mechanism is provided to counterbalance the weight of the occupant of the seat, so that movement of the seat in an upward direction is effected automatically when one or both the linear positioning devices are unlocked, provided that the occupant of the seat reduces the downward force applied to the seat to less than the upward force provided by the bias mechanism. Adjustment in a downward direction is effected when one or both of the linear positioning devices are unlocked and sufficient weight is applied to the seat to provide a downward force sufficient to overcome the bias mechanism.

Preferably, the bias mechanism is provided independently in each linear positioning device 70, 80, as a compression spring which is coaxial with the shaft 74, 84 around which it resides. The compression spring bears against the moving end 71 , 81 and the casing 73, 83 of the linear positioning device 70, 80 such that when the locking mechanism is released, the device expands in length. For clarity, the compression spring 89 is shown in figures 1 and 2 only in respect of the second linear positioning device 80, although it will be understood that a similar arrangement is provided on the first linear positioning device 70.

If appropriate, the first and second linear positioning devices may be provided with different strengths of compression springs to provide differing amounts of uplift to the front and back part of the seat, to allow for normal weight distribution of the occupant during the adjusting exercise.

Both the first and second linear positioning devices 70, 80 are preferably each provided with an independent flexible control cable 90, 95 operating in like manner. The flexible control cables 90, 95 lead to an actuating lever or pair of levers (not shown).

In the preferred embodiment, a single lever is provided in which operation of the lever in a first direction from a central (home) position pulls on the control wire 91 of the first control cable 90, while the control wire 96 is permitted to free-run through the lever and is thus not actuated. The first linear positioning device 70 is thereby unlocked, and the height of the front of the seat may be adjusted. Return of the lever to the home position is automatic by way of a suitable spring bias, and locks the device 70. Operation of the lever in the opposite direction from the home position pulls on the control wire 96 of the second control cable 95, while the control wire 91 is permitted to free-run through the lever and is thus not actuated. The second linear positioning device 80 is thereby unlocked, and the height of the aft portion of the seat may be adjusted. Return of the lever to the home position is automatic by way of a suitable spring bias, and locks the device 80.

It will be understood that various types of actuating levers or control devices are possible, including a separate lever for each linear positioning device.

A significant benefit of the height and tilt adjustment mechanism described above is that it is quickly and easily adjustable to obtain both the desired height and the desired degree of tilt of the seat using only a single control lever. This is of particular utility in commercial vans where the vehicle may be used by many different drivers throughout the working day, thereby making complex adjustment mechanisms tedious to use and likely to be ignored resulting in poor driving position.

While automated seat positioning systems are known, these are complex and expensive. A further benefit of the present height and tilt adjustment mechanism 10 is its low cost design, using identical component assemblies for both the forward and aft height adjustment mechanisms. With the exception of the third and fourth link members 55, 56 being provided with slots 58 (which actually form part of the seat base frame 15), all components can be made identical for forward and aft use.

A further advantage of the height and tilt adjustment mechanism 10 is its low profile. Particularly in some types of commercial vehicle, where the front seating resides over wheel arches, over the engine bay, or over a housing for other equipment such as the battery, it is important to reduce the depth of the seat adjustment mechanism to a minimum, while simultaneously offering as much height adjustment as possible. The present design provides the height adjustment mechanism which resides entirely beneath the seat, predominantly within the depth of the seating slides. A large vertical travel is possible by efficiently translating the large horizontal expansion of the linear positioning devices into vertical motion through the crank 40, 50 design.

Although the crank assemblies 40, 50 have been shown as including a crank bar 41, 51 with a laterally displaced intermediate portion 44, 54, it will be understood that this could be replaced by a straight bar with a further arm extending laterally from the crank bar axis, or by a number of other crank configurations well understood in the art.